How do you prevent authorities or malicious actors from snooping through your laptop or other belongings when you're not around? Surveillance whistleblower Edward Snowden and his associates say the answer is an app that lets you spy back on the spies.

Just before Christmas, Snowden, the Freedom of the Press Foundation, and the Guardian Project announced the release of an Android app called Haven. Available in beta, the open source software turns the many sensors found in a typical smartphone into a security system that "watches" its surroundings and lets the phone's owner know when someone has gained unauthorized access to that person's possessions.

Haven is designed for journalists, human rights activists, and others who are concerned about protecting their personal spaces and devices from intrusion, whether it's by nosey housekeepers, thieves, police, or intelligence agencies. The Android app not only detects unwanted visitors but notifies the phone's owner with text alerts and encrypted records of everything the device's sensors have logged.

'A Kind of Herd Immunity'

"When you think about a smartphone today, they've got an incredible amount of surveillance equipment that is built into them: typically, two cameras, they've got three microphones, they've got barometers, accelerometers, light sensors, always-on Internet connection," Snowden said in a video accompanying Friday's announcement about Haven. "They have the power to understand everything that's going on around them."

Once installed and activated on a phone left behind in a user's personal space, Haven uses all of the device's built-in sensors to detect any changes in the surroundings, whether that's a light being turned on or off, the sounds of someone entering the room, or an intruder passing in front of the phone's camera. When any such activity is detected, the app instantly sends a text notification to the owner's main phone. The owner can then use Signal or the Tor onion service to securely and remotely access all of the Haven surveillance data stored on the phone.

"Haven makes it harder to silence citizens -- raids, searches, arrests -- without getting caught in the act themselves," Snowden said. "This creates a kind of herd immunity where, before people launch a crackdown, they have to think, 'Will I be witnessed in a way that I can't stop?' . . . Haven does more than watch your back: it gives you peace of mind."

Phone-Based Honeypot

Since revealing a large amount of classified information in 2013 about how surveillance organizations use Internet and mobile technologies to spy on citizens in the U.S. and elsewhere, former National Security Agency contractor Snowden has been living in exile in Moscow. While there he has been working with organizations, such as Freedom of the Press Foundation and the Guardian Project, on privacy, security, and free speech issues.

Founded in 2012, the Freedom of the Press Foundation is led by Snowden, Pentagon Papers whistleblower Daniel Ellsberg, and journalist/activists, including Glenn Greenwald, Laura Poitras, and Trevor Timm. The Guardian Project, founded by Nathan Freitas in 2009, is a global organization of developers, designers, and activists who create open source software for mobile privacy, security, and encryption. It describes Haven as a phone-based honeypot for "people who want to keep an eye out for intrusions into their home, office, hotel room or other private space."

In addition to seeking donations to support further development of Haven, the Freedom of the Press Foundation and the Guardian Project are asking testers, developers, and others to help work on the app and build the Haven community.